The disclosure relates to a xerographic printing machine, and more particularly, to an image forming machine having marking engines with a low gloss and a high gloss developer for the same color.
A typical electrophotographic, or xerographic, printing machine employs a photoreceptor, that is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoreceptor is exposed to a light image of an original document being reproduced. Exposure of the charged photoreceptor selectively dissipates the charge thereon in the irradiated areas to record an electrostatic latent image on the photoreceptor corresponding to the image contained within the original document. The location of the electrical charge forming the latent image is usually optically controlled. More specifically, in a digital xerographic system, the formation of the latent image is controlled by a raster output scanning device, usually a laser or LED source.
After the electrostatic latent image is recorded on the photoreceptor, the latent image is developed by bringing a developer material into contact therewith. Generally, the electrostatic latent image is developed with dry developer material, referred to as toner, comprising toner particles which are attracted to the latent image, forming a visible powder image on the photoconductive surface. After the electrostatic latent image is developed with the toner particles, the toner powder image is transferred to a sheet, such as paper or other substrate sheets, using pressure and heat to fuse the toner image to the sheet to form a print.
Color prints are formed in this manner using one or more color separations. A different color toner, also referred to as a colorant, is applied and developed for each color separation and the color separations and then combined to form the resulting color print. A monochrome image is formed of one color separation, typically black. Process color images are typically constructed of separate cyan, magenta, yellow, and black (CMYK) separations. Extended colorant set images typically include the process-color colorant separations (CMYK) plus one or more additional colorant separations such as green, orange, violet, red, blue, white, varnish, light cyan, light magenta, gray, dark yellow, metallics, and so forth.
Toner has several fused characteristics which determine qualities of the resulting image print. The color a toner produces in a print is one characteristic. Another, is the gloss level of the fused toner in the print, also referred to as gloss. Toners typically produce a fairly consistent gloss level, with high gloss toners being used to produce glossy prints and low gloss toners being used to produce low gloss, or matte, prints.
It can be desirable to manipulate the gloss of printed images. In an xerographic system using a given print medium, the gloss level of a printed image for a given toner depends on fusing parameters, also referred to as set points. These set points can include the fusing time, which is the contact time spent between the fusing rollers, the fusing speed, the contact length which is the length of the nip defined by the pressure roller pair of the fixer, the fusing temperature, and the oil quantity applied to the outer circumference of the rollers. U.S. Pat. No. 6,101,345 to Van Goethem at al. teaches a method of varying the gloss level a particular toner can produce in a print by changing these fuser set points so that fusing at a high speed and at a lower fusing temperature results in a lower gloss, and fusing at low speed and at a higher temperature results in a higher gloss, for a specific print medium. However, this technique can be slow to respond and offers a rather limited range of gloss variation of a given toner.
Others have taught using more than one toner, each producing a different gloss level in the printed image. U.S. Pat. No. 7,630,669 to Banton, discusses using multiple black developer systems, each having black toner with different gloss characteristics, to produce low-cost-per page black and white prints. US Publication No. 2008/0240788 to Mashtare, et al. teaches using a xerographic tri-level process using a single charge and developments stations and two developers systems on a single PR drum wherein the second developer system can include the use of a clear toner with a gloss or matte finish. This toner does not have a color and serves as a coating which can change the gloss of the underlying text, picture or graphic.
It is, however, desirable for a xerographic image forming machine to provide greater control over the range of gloss levels available in the printed color image.